Thyroid nodules: When is an aggressive evaluation warranted?

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Applied Evidence

Thyroid nodules: When is an aggressive evaluation warranted?

J Fam Pract. 2012 April;61(4):205-208

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References

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Who is a candidate for fine-needle aspiration?
FNA is unequivocally the most cost-effective tool for establishing the benignity or malignancy of a thyroid nodule. Its estimated sensitivity is 83%, specificity is 92%, and positive predictive value is 75%.⁷ Selecting nodules and biopsy technique appropriately can decrease sampling error. Nodules that are purely cystic and those that appear “hot” on radioactive iodine scanning do not require sampling. Neither do nodules <1 cm in diameter that lack features associated with malignancy. However, any nodule >5 mm in diameter with high-risk or otherwise suspicious features (eg, microcalcifications, irregular margins) on ultrasound are candidates for FNA.⁶

With the exception of easily palpable nodules, ultrasound imaging is widely used to guide biopsy (UG-FNA) so as to minimize the rate of nondiagnostic samples. Historically, less than 10% of FNA results are malignant and 60% to 80% are confirmed benign.⁶

Management decisions

Confirmation of a benign nodule obviates the need for surgical resection, although follow-up is required with serial ultrasound evaluations to assess any increase in size. Slow growth is the natural history of thyroid nodules,²³ and there are no clear data to indicate a rate or degree of growth suggestive of malignancy.²⁴ Order a repeat ultrasound examination 6 to 18 months after the initial evaluation. Should a nodule show more than 50% change in volume (20% change in 2 dimensions), consider referring for UG-FNA⁶ or surgical resection.⁷ Referral for surgical resection is also warranted if compressive symptoms occur despite a nodule’s benign nature. A meta-analysis of the use of levothyroxine supplementation to prevent nodular growth did not show a statistically significant effect, although a trend toward shrinkage was noted.²⁵

A clear diagnosis of malignancy on FNA necessitates a surgical referral for total thyroidectomy, as well as an endocrinology consultation for possible postoperative radioactive iodine remnant ablation and thyroid hormone replacement. Suspicious cytology results and follicular lesions in the presence of normal thyroid function usually require surgical resection due to high rates of malignancy confirmed postoperatively (60% and 20%, respectively).⁶

FAST TRACK

Ultrasound is the imaging method of choice for thyroid nodules; CT, MRI, and other modalities are not cost effective.

If the FNA result is nondiagnostic on the first attempt, a second attempt is warranted, preferably under ultrasound guidance (UG-FNA) to improve yield. A second nondiagnostic sample is an indication for surgical resection. Up to 12% of such scenarios lead to histologically confirmed malignancy postoperatively.⁶

Radioactive iodine therapy is commonly used to treat hyperfunctioning “hot” nodules, yielding a rate of return to normal function between 85% and 100%, and a median reduction in size of 45% at 2 years.⁶ Using radioactive iodine to treat nodular disease in euthyroid individuals with normal uptake on a scan had variable results, with 20% of patients having no change in nodule size and 80% having up to a 60% decrease in size at 5 years.⁶ Large-scale studies are needed to compare radioactive iodine therapy with surgical resection.

CORRESPONDENCE Armand Krikorian, MD, Division of Clinical and Molecular Endocrinology, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106; armand.krikorian@UHhospitals.org